This invention relates generally to radiotelephones and, in particular, to radiotelephones or mobile stations capable of operation with a digital cellular network.
The so-called Short Message Service (SMS) is a point-to-point service which enables a user to send messages to and receive text messages from other users of a communications network. The SMS attempts to deliver a message to a mobile terminal whenever the terminal is registered to the network, even when the terminal is engaged in a voice or data call. The terminal may also roam throughout the network and still be capable of sending and receiving messages. A terminal configured for SMS provides methods for the user to receive, read, write/edit, clear, send, and save messages. The connection of a standard keyboard to the terminal facilitates the generation and editing of text messages by the user.
The network stores messages in at least one Message Center (MC), and Mobile Terminated (MT) messages are sent to the terminal by an MC. Various SMS protocol layers receive the messages and check their contents. If the contents are valid, and assuming that there is room for incoming text messages in the memory of the terminal, the message is received and stored. Otherwise, the message is rejected.
U.S. Pat. No. 4,644,351 (Zabarsky et al.) discloses a paging system that enables messages to be sent to a remote unit, and which has a capability for the remote unit to transmit a message-received acknowledgement signal back to a central site. The paging system of Zabarsky et al. also enables a message-presented verification to be transmitted from an addressed pager back to the central site.
Reference can be had to the TIA Interim Standards IS-136 and IS-137, and also to a document entitled xe2x80x9cTDMA Forum, Implementation Guide: Short Message Terminals Compliant With IS-136 and IS-137xe2x80x9d (Ed. D. Holmes, vers. 7.0, Apr. 20, 1995). These documents specify one type of SMS and the various system and terminal level protocols required to provide SMS. This latter document describes in sections 3.2.1 and 3.2.2 a Delivery Acknowledgement and a Manual Acknowledgement capability, respectively. By example, a message xe2x80x9cCan you meet me this evening?  less than NTC greater than Yes less than NTC greater than Noxe2x80x9d, where NTC is a non-text character, is said would allow the user to select a response from xe2x80x9cYesxe2x80x9d or xe2x80x9cNoxe2x80x9d, and consequently cause the terminal to send response codes 0 or 1.
Another type of SMS is known as broadcast SMS (or also as S-BCCH), which is a point-to-multipoint operation (i.e., from a network operator to a plurality of mobile stations). Reference may had to, by example, a publication entitled xe2x80x9cS-BCCH for IS-136xe2x80x9d, TR45.3.6/95.06.13/8, Digital Cellular Systems, Jun. 12-15, 1995 (Ericsson).
The Short Message Service Broadcast Channel (S-BCCH), in the IS-136 specification, is specified for use in sending short point-to-multipoint messages to mobile stations, such as radiotelephones. A maximum number of 15 slots per superframe may be assigned to the S-BCCH logical channel. The S-BCCH is considered as a continuous channel even if more than one slot is allocated to the S-BCCH. The IS-136 rev. 0 specification does not specify particulars of this mode of operation, except for the layer 2 reservation of slots within a superframe.
One possible implementation for such a system is as follows. This implementation is similar to that originally set forth in the preliminary IS-136 rev. 0 specification.
The SMS frame can be defined as a sequence of 24 Superframes which are aligned with a Hyperframe (HF) counter. Thus, the number of slots assigned to the SMS frame are 0, 24, 48, 72, depending on how many slots per superframe are assigned to BCCH.
The Hyperframe (HF) counter and a Primary Superframe (SF) indicator can be provided in the BCCH. These two counters together (2*HF Counter+Primary SF indicator) constitute a Superframe counter. A SMS frame is defined to be a single complete cycle (0-23) of the SF counter. The SMS frame is aligned to start at a HF counter value of 0, and also when the Primary Superframe indicator equals 0. The SF counter provides SMS frame synchronization information to the mobile station.
SMS subchannels are defined to allow different repetition cycles for different messages. Each subchannel has its own repetition cycle defined in terms of units of SMS frames. SMS frames are grouped into the SMS subchannels. Within each subchannel, a repetition cycle is defined (in units of SMS frames) with which the SMS broadcast message sequences contained in the SMS sub-channel are repeated. The SMS broadcast subchannel cycle may range from 1 to 64 SMS frames in length. Within each subchannel, the first S-BCCH slot within each SMS frame contains a header that describes the structure of the subchannel. Up to four subchannels may be defined. If more than one subchannel exists, the subchannels are time-multiplexed onto the S-BCCH channel on a SMS frame basis. If a SMS subchannel block is defined to consist of one SMS frame from each subchannel, placed in ascending order of subchannel number, then the multiplexed subchannels can be defined as the repetition of these subchannel blocks. The number of subchannels and the identity of the subchannel to which an SMS frame belongs are specified in the SMS frame header.
According to SMS header information found in the first slot in any SMS frame, the set of messages in SMS(i) may span M(i) number of SMS frames before a cycle is completed. M(i) is the length of the sub-channel cycle. The SMS frame number within the subchannel cycle is referred to as the phase of the subchannel cycle.
A number of different BCCH message categories can be defined. These include Emergency Information messages, Time and Date messages, Overload Class messages, System Identity messages, and Broadcast messages. Each BCCH message typically includes a number of fields of information. These fields can include: a Protocol Discriminator field (2 bits), a Message Type field (6 bits), a SMS Message ID field (8 bits), and a Text Message Data field (8 to 2024 bits).
The Broadcast Message category field is coded to provide a number of different types of message category identifiers. These include, by example, emergency numbers and road-side information, toll gate information, airline departure/arrival information, weather-related information, news, and financial information.
What is not currently provided, and what is thus an object of this invention, is a signalling capability that selectively enables a mobile station that receives a broadcast SMS message to reply to the message.
It is thus a first object of this invention to provide an improved method for providing broadcast SMS in a digital cellular system, wherein a point-to-multipoint message can be responded to in a point-to-point manner.
It is a second object of this invention to provide an improved method for providing broadcast SMS in a digital cellular system, wherein a point-to-multipoint message can be responded to by a mobile station originating a call to a call-back number that comprises a part of the broadcast SMS message.
It is a further object of this invention to provide an improved method for providing broadcast SMS in a digital cellular system, wherein a point-to-multipoint message can be responded to by a mobile station generating a manual acknowledgement message.
The foregoing and other problems are overcome and the objects of the invention are realized by methods and apparatus in accordance with embodiments of this invention.
A method of this invention is disclosed for operating a cellular communications system of a type that comprises a Base Station/Mobile Switching Center/Interworking function (BMI) and a plurality of mobile stations. The method includes the steps of transmitting a point-to-multipoint message (e.g., a Broadcast SMS message) from the BMI to the plurality of mobile stations; and, in at least some of the plurality of mobile stations, receiving the point-to-multipoint message and transmitting an acknowledgement to the BMI using a point-to-point message.
The point-to-multipoint message includes an information element having a value for specifying one of (a) that a mobile station receiving the message is prohibited from responding to the message, (b) that a mobile station receiving the message must respond to the message, and (c) that a mobile station receiving the message may optionally respond to the message. Mobile stations receiving the message selectively respond or not respond to the message, at least as a function of the value of the information element.
The method further includes an initial step of transmitting a message to the plurality of mobile stations, the message including an information element for specifying that the BMI is capable of transmitting a point-to-multipoint message.
In one embodiment of this invention the step of responding includes a step of generating and transmitting a manual acknowledgement message, while in another embodiment the step of responding includes a step of originating a call to a telephone number that forms a portion of the point-to-multipoint message.
In a preferred embodiment of this invention the steps of transmitting and responding each use an R-Data message or equivalent, as especified in IS-136 or similar air interface standards.
The use of this invention enables a network operator to poll a plurality of mobile stations, at a cell level or higher (e.g., a SID level), so as to elicit a response to an issue presented in the point-to-multipoint message. In this manner the user""s of the mobile stations may vote on an issue presented for consideration.
The use of this invention furthermore enables a network operator, or some other entity, to offer goods or services through the point-to-multipoint message, and to respond to acknowledgement messages transmitted from mobile stations having user""s that wish to avail themselves of the offered goods or services.